1. Field of the Invention
The present invention relates to an air intake device for a straddle-type vehicle such as a straddle-type four-wheel vehicle or a motorcycle.
2. Description of the Related Art
A straddle-type vehicle is provided with some apparatuses which utilize intake air taken from ambient air. A typical example of this kind of apparatuses is an air cleaner which takes in air for burning in an engine. Other examples are a cooling apparatus which takes in cooling air for a transmission and a breather apparatus for a crank case, etc. All of these apparatuses are provided with air intake portions, respectively.
FIG. 10 shows a known straddle-type four-wheel vehicle having an air intake device (JP-A 2001-221113). The four-wheel vehicle includes a body frame 101 which is provided with a pair of left-and-right front wheels 102 and a pair of left-and-right rear wheels 103. An engine 105 is disposed between the front and rear wheels. A carburetor 116 is disposed above the engine 105 and a air cleaner case 121 of an air cleaner 120 is disposed above the carburetor 116. An air intake duct 118 is mounted on the front end of the air cleaner case 121. The air cleaner case 121 and the carburetor 116 are covered with side covers 113 at their left-and-right sides. The upper part of the air cleaner case 121 is covered with a decorative cover 115. Fenders 110, 111 are disposed above the front and rear wheels 102, 103, respectively. A seat 108 is disposed behind the cleaner case 121. A steering shaft 107 having a steering handlebar 106 at the upper end thereof is disposed in front of the cleaner case 121.
A transit chamber 126 for air intake, which is covered with a front cover 119, is formed above the steering shaft 107. An air intake duct 118 connected to the air cleaner case 121 is extending frontward and upward to the transit chamber 126 so that the upper end of the air intake duct 118 opens in the transit chamber 126.
When ambient air is taken-in in a straddle-type vehicle, an air intake port is preferably disposed at a position as high as possible to prevent water and mud from entering the air intake port. Moreover, the air intake port is preferably covered with a covering member for protection against dust. Accordingly, the air intake duct 118 is extended upward as high as possible, and the upper end thereof opens in the transit chamber 126 which is covered with the front cover 119.
A V-belt continuously variable transmission, not shown, is mounted on the right side of the engine 105. A cooling air intake duct of the transmission is extending upward in front of the engine 105 to the transit chamber 126 so as to open in the transit chamber 126.
FIG. 11 shows another known related art in which an air intake duct 201 of an air cleaner is extended upward and the open upper end of the air intake duct 201 is covered with a cup-shaped cover 202.
In the constitution shown in FIG. 10, a space for disposing the upward extending air intake duct 118 and a space for forming the transit chamber 126 are required so that the size of the vehicle inevitably becomes large and also the number of parts for the air intake device inevitably becomes large.
The constitution shown in FIG. 11 also requires a space for disposing the long air intake duct 201 extending upward. Moreover, an annular air intake port 203 is formed between the outer circumferential surface of the air intake duct 201 and the inner circumferential surface of the cup-shaped cover 202, and the diameter of the air intake duct 201 is limited. Therefore, in order to enlarge the area of the annular air intake port 203, the size of the cup-shaped cover 202 should be enlarged so that the weight of the air intake device inevitably increases.